This study develops a theoretical explanation for the existence of positive, as well as negative, experience spillovers across organizational activities. The authors suggest that the perceived similarity in two activities influences both the sign and magnitude of experience spillovers. The argument is then used to understand whether and how alliance experience influences acquisition performance. The empirical evidence indicates that the spillover effect is a function of the decisions made in the post-acquisition phase regarding the level of integration and the degree of relational quality among the two firms. Implications of these findings are drawn for our understanding of organizational learning and evolutionary processes in a multi-task context.